Abstract
Nano-granular thin films with a new composition designed to enhance the tunneling magneto-dielectric (TMD) effect of Co–SrF2 were successfully deposited using the co-sputtering method. This study explored the influence of the crystallinity of the matrix material on nano-granular structures. Cobalt contents were controlled from 0 to 19 at. % by changing the power of the cobalt cathode from 0 to 205 W. The structures in which the Co granules (Φ 3–4 nm) were homogeneously dispersed in the crystallized SrF2 matrix were clearly observed by transmission electron microscopy and its diffraction patterns. The dielectric constant of the Co19–(SrF2)81 thin film peaked at the giant value of 648 and the saturation magnetization peaked at 3.1 kG, but this material still exhibited a TMD response Δε′/ε′0 of 1.0%. For the Co16–(SrF2)84 thin film, the TMD response peaked at 3.5%, which is higher than previously reported. This study confirmed that increased matrix crystallinity can enhance the TMD response. It also provides motivation for other microstructure improvements.
Highlights
In the age of the internet of things, applications of magnetoelectric (ME) and quantum effects have experienced explosive growth
As the Co content approached 19 at. %, the Co granules became elliptical along the film growth direction and their TEM images probably overlapped
TEM, magnetization, and permittivity results all showed that two states existed: with a Co content below 9 at. %, the Co granules were not formed well and MS, ε′f=1kHz, and ε′f=1MHz increased to 0.55 kG, 26, and 5, respectively; when the Co content doubled to 19 at. %, the number of granules increased and these parameters increased to 3.1 kG (5× increase), 648 (25× increase), and 139 (28× increase), respectively
Summary
In the age of the internet of things, applications of magnetoelectric (ME) and quantum effects have experienced explosive growth. The design that couples magnetic and dielectric properties through a certain property, such as crystal symmetry, enlightened subsequent research of the MD effect with various mechanisms, such as spin–orbit coupling, spin–lattice coupling, Jahn–Teller distortion with spin–orbit coupling, coupling of uniform polarization and q-dependent spin–spin correlation, and unusual commensurate–incommensurate magnetic transition coupling.. The design that couples magnetic and dielectric properties through a certain property, such as crystal symmetry, enlightened subsequent research of the MD effect with various mechanisms, such as spin–orbit coupling, spin–lattice coupling, Jahn–Teller distortion with spin–orbit coupling, coupling of uniform polarization and q-dependent spin–spin correlation, and unusual commensurate–incommensurate magnetic transition coupling.14 Their chemical compositions were limited to oxides, especially manganate, and high crystallinity is indispensable. In terms of applications, the largest limitation was the very low operating temperature
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